UPon first windows installation, create 2 partitions, each of whatever size you like.

Install to the first partition.

Update windows, blah, blah, drivers, blah blah.

Once windows is updated, from your desktop, install windows again(2nd version), selecting the blank partition as the target drive.

UPon starting windows, you should be greated with a "boot loader" that allows you to select which OS you boot to.

If not, go into whatever windows you are "allowed" into.

open an explorer window, and go to "folder options" inside one of the "ALT" menus(TOOLS) at the top of the explorer window.

Inside the folder options, there should be a tab called "VIEW". Select the option "show hidden files and folders". Unselect the option for "hide protected system files" here as well as "show extenesions for known file types", and then press "apply to all folders" at the top of the "option's" "VIEW" window.

Navigate to "C:\"(or whatever letter your harddrive is)

look for "boot.ini", and rightclick it and open using "notepad".

Inside you'll find a long line at the bottom denoting the operating system it's booting from.

Select this entire line, copy it, and then paste it below the original.

If using just a different partition, you'll see this noted in this line you jsut copied. if the exisiting line says "PARTITION 0", then you are booting from your first windows.

IF it says "PARTITION 1", you are booting form the second partition.

Modify the number following "PARTITION" in the line you pasted to the correct partition on which your other windows is located (in hexadecimal, where we start with 0, and not start with 1!!!)

further down that line, you'll see "Microsoft Windows XP HOME Edition" or some such drivel. It will be the same on each line(original, and the one you pasted), and the original line is the windows you are currently using, the bottom is the one you first installed, so please feel free to modify whatever is within those "quotes" so you know which OS you are booting from.